1. Field of the Invention
The invention relates generally to railroad signaling systems and methods. More particularly, the invention relates to systems and methods for detecting and reporting incorrect operation of cab signal track circuits.
2. Description of the Prior Art
Railroad signaling has traditionally been based upon a concept of protecting zones of track, sometimes called xe2x80x9cblocks,xe2x80x9d by means of some form of signal system that conveys information to the locomotive engineer about the status of the blocks of track ahead. Typically, wayside signal lights are located along the track and are controlled by electrical logic circuits responsive to the presence of railway vehicles and the status of blocks that are relevant to a given wayside signal. In such systems, each wayside signal typically displays a pattern of lights, called the xe2x80x9caspectxe2x80x9d of the signal, which is visible to the engineer in the locomotive and indicates the status at that location.
A more advanced signaling system in widespread use is referred to as cab signaling and may be used with or without wayside signal lights. In cab signaling, the same or similar logic that determines block status for display on the wayside signals is also used to generate one of several forms of encoded signals (e.g., encoded electrical current signals) carried in the rails, block status being represented by the selection of the code rate used. Inductive pickup coils are mounted on the locomotive ahead of the lead wheels and just above the rails for the purpose of sensing the magnetic fields around the rails produced by the encoded current. In modern systems, a computer on-board the locomotive decodes the detected information to determine the status and thereafter displays the proper aspect in the engine cab by a pattern of lights in a manner similar to a wayside signal. One advantage, of course, is that the information is made available to the train crew on a continuous basis and updated when changes in status occur, rather than restricting the communication of status information to periodic intervals along the track at which the engineer is required to observe and read the next wayside signal.
The detectors or pickup coils typically used in on-board cab signal systems are iron core or ferrite core inductors employed in pairs, one being mounted above each rail. The carrier frequency of the cab signal is typically in the range of from about 40 Hz to 100 Hz but may be higher. For example, the carrier frequency may be in the kilohertz range such as 4,550 Hz. In other systems, the operating range for cab signal is 73 Hz to 100 Hz. In yet other systems, the range of 78.3 Hz to 88.3 Hz is considered a good operating range for a cab signal. Different modulation rates are used to convey different states that are converted in an on-board computer to cab signal aspects. Modulation rates for the cab signal and corresponding aspects are well known in the prior art. For example, in one prior art system modulation rates for the 40 Hz carrier are slower than some of those used at higher frequencies, because of the ringing effects of the large filters needed to couple 40 Hz to the track and block other frequencies used for grade crossing equipment. Suggested rates for a 40 Hz carrier and the aspects associated with each range are from the fastest rate of 75 pulses per minute (ppm) to the slowest of approximately 27 ppm. The modulation is generally non-symmetrical in that the xe2x80x9coffxe2x80x9d time of all rates below 75 ppm is the same, 600 milliseconds. In one embodiment, the cab signal parameter that is encoded in the cab status signal indicates a status of xe2x80x9crestrictingxe2x80x9d where the modulation rate is 0, a status of xe2x80x9capproach stopxe2x80x9d where the modulation rate is 75 ppm, a status of xe2x80x9capproach restrictingxe2x80x9d where the modulation is 32 ppm, a status of xe2x80x9capproach divergingxe2x80x9d where the modulation rate is 39 ppm, a status of advance approachxe2x80x9d where the modulation rate is 27 ppm, and a status of xe2x80x9cclearxe2x80x9d where the modulation rate is 50 ppm.
If the equipment used to generate the cab signal in the rails is malfunctioning or operating marginally, the on-board display will generally show a restrictive indication in the locomotive cab. This will cause the train to be slowed to a restricted speed until a track circuit block with correctly operating cab signals is reached. The slowing of trains in inoperative track circuit blocks can cause undesirable train delays. In the worst case, an unexpected restrictive aspect can contribute to the risk of train derailment, such as when the train is required to slow from a high speed to restricted speed in a curved section of track.
Currently, the locomotive operating crew monitors the on-board aspect display and identifies unexpected indications when they occur. When these indications are observed, the cause is generally not known. The crew reports the unexpected indication that may be addressed at the next scheduled maintenance opportunity for the locomotive. Without further diagnostic capabilities, the unexpected indication may be a correct indication caused by movements of trains or switches ahead, or may be due to a failure of the on-board cab signal detection equipment or a failure of the track circuit. However, in some cases, where a restrictive aspect might be expected by the train crew, and no wayside signal lights are visible, failure of cab signal track circuits will not be noticed or reported by the crew.
Therefore, there is a need for a system and method for detecting an incorrect operation of failed or marginally operating cab signal track circuits and/or cab signal display system so that such failures and marginal operating conditions may be identified and repaired in a timely manner. Advantageously, such a system and method could be automated to improve the reliability of reporting cab signal problems and to reduce the labor associated with reporting such problems. Further, such a system and method could be used to provide an accurate indication of the cause of a particular cab signal problem and distinguish between track circuit failures and failures associated with equipment on-board a locomotive. Such a system and method could also improve the timeliness and/or effectiveness of repairing cab signal problems. For example, a repair crew could be automatically dispatched and provided with information regarding the type of problem detected and the type of equipment and parts likely required to correct the detected problem. Likewise, the repair crew can use a similar system and/or method to detect when it has encountered the failed track circuit and when the failed circuit has been restored to proper operation.
In one form, the invention relates to a railroad cab signal quality detection system for use in connection with a railroad cab signaling system in which a status signal is carried on a railroad rail. The status signal may include an encoded cab signal parameter that is indicative of a status of a zone of track. A signal detector detects the status signal transmitted via the railroad rail. A signal measurement subsystem is associated with the signal detector and measures the cab signal parameter. A quality analysis subsystem analyzes the measured cab signal parameter and determines a measure of the quality of the cab signal parameter.
In another form, the invention is a railroad cab signal quality collection and reporting system for use in connection with a railroad cab signaling system. In this form, the invention includes a data collection system that collects data indicative of a measure of a quality of the cab signal parameter of the status signal. A quality analysis and reporting system analyzes the collected data and generates reports responsive to the collected data and indicative of the measure of quality of the cab signal parameter.
In yet another form, the invention is a system comprising a locomotive, a cab signal detector, a cab signal conditioner, a cab signal converter, and a cab aspect display system. A signal measurement subsystem is associated with the cab signal detector and measures a cab signal parameter. A quality analysis subsystem analyzes the measured cab signal parameter and determines a quality of the cab signal parameter. A reporting subsystem receives the determined quality of the cab signal parameter from the quality analysis subsystem. The reporting subsystem generates a report containing the received determined quality.
In another form, the invention is a railroad cab signaling system comprising a cab signal parameter and a cab signal transmitter for transmitting a status signal onto a railway rail. This form of the invention also includes a signal detector for detecting the status signal transmitted via the railroad rail. A signal conditioner conditions the status signal detected by the signal detector and provides a conditioned cab signal. A signal converter associated with the signal conditioner receives the conditioned cab signal and converts the conditioned cab signal to a digital cab signal. A signal measurement subsystem measures a cab signal parameter from the digital cab signal. A quality analysis subsystem analyzes the measured cab signal parameter and determines a measure of quality of the cab signal parameter. A reporting subsystem receives the determined measure of quality of the cab signal parameter from the quality analysis subsystem and generates a report containing the received determined quality.
In another form, the invention is a quality monitoring method for use with a railroad cab signaling system in which a status signal is carried on a railroad rail. The status signal includes an encoded cab signal parameter that is indicative of a status of a zone of track. The quality monitoring method comprises detecting the status signal. The cab signal parameter is measured from the detected status signal. A measure of quality of the measured cab signal parameter is determined. The determined measure of quality of the measured cab signal parameter is reported.
These and other forms of the present invention will become more apparent and in part pointed out hereinafter.